1)while takeing of full backup of SQL DATABASE it takes transacation logs also for backup but it can not truncate why?
log trunction is done by sql, when logs are backed up they are only marked for truncation, netbackup doesnot truncate the logs its SQL application which needs to do it, if that is not happening please check the event viewer for more details, if you have SQL clsuter or so where it is waiting for logs to be replicated in that scenario aswell it will not truncate the logs immediately.
2)it is possible take only database for backup instead of logs. after that we can resotre the database without logs
SQL logs are written to .lDF file which is part of database, hence when you backup SQL it will backup .mdf and .LDF, there is an option to backup only logs however not the database.
3)while taking differential backup of sql database logs will get truncate or not? if it will clear the logs which type of differential backup need to be configure like cumulative or incremental
no they will not, you can only perform full, differential backup i.e cumulative incremental backup and transaction log backup of SQL database, in netbackup
please refer to the article http://www.veritas.com/docs/000029573 for more details.
4)I have a 3 full backup of SQL databases in such a case 3rd full backup is currpeted then we can restore the 1st and 2nd full backup along T-logs related to all 3 databases
as mentioned above SQL logs are stored in .ldf file if third full backup is corrupt, max you can go back to 2nd full and than restore differential if you have taken any in between 2nd and 3rd backup.
